Microbiology - Respiratory Tract Infections Flashcards
What are our defence mechanisms against respiratory tract infections? Large bacteria? Small bacteria?
Large bacteria: caught in the mucus layer. Cilia on the mucous membrane move bacteria to back of throat (are then swallowed).
Small bacteria: alveolar macrophages phagocytose + lyse them.
What are the general virulence factors for bacterial respiratory tract infections? (3)
- Attachment to mucosa by attachment factors (so they are not swept away by cillia)
- Inactivation of cillia (bacteria can then multiply at site of infection)
- Reproduction w/in macrophages - macrophages provide a safe haven for replication
What are the upper respiratory tract infections? (6)
SOOPLE
Sinusitis Otitis Media Oral Cavity Infections Pharyngitis Laryngitis Epiglotitis
What are the lower respiratory tract infections? (8)
BALD PCTC
Bronchitis Anthrax Lung Abscess Diphtheria Pneumonia COPD Exacerbation Tuberculosis Cystic Fibrosis
What is bacterial sinusitis?
It is the inflammation of sinuses due to bacterial infection?
How do the sinuses become infected?
The sinuses are usually sterile due to mucus flow through the ostia to nasal cavity. What happens, the ostia become obstructed (due to viral infection or allergies) and this blocks the sinusitis allowing for mucus to accumulate and cause infection.
What are the SX of bacterial sinusitis?
Thick, purulent nasal discharge, congestion, facial pain and headache. (Less common SX - toothache and halitosis)
How is bacterial sinusitis caused? What are some bacteria that cause bacterial sinusitis? What characterizes the nosocomial infections?
It is caused by the overgrowth of organisms normally found in the nasopharynx.
S. pneumonia
H. influenza (non-encapsulated)
Moraxella catarrhalis (mostly children)
Nosocomial infections (are polymicrobial, multiple-drug resistrant strains)
How do you treat bacterial sinusitis?
Amoxicillin
What is the physiology and structure of moraxella catarrhalis? Where is it normally found?
Gram negative diplococcus (other is neisseria meningitidis).
Normally found in nasopharynx (more common in children)
What diseases are caused by moraxella catarrhalis? (3)
Otitis media
Sinusitis
Pneumonia (immunocompromised/COPD patients)
How do you treat moraxella catarrhalis?
Antibiotics - depends on site of infection and other possible bacteria present.
What is otitis media and its pathophysiology?
It is inflammation of the middle ear.
It occurs by blockage of the eustachian tubes in which sterile fluid accumulates in the middle ear allowing for bacteria from the nasopharynx to grow.
NOTE: Most acute otitis media follows viral URTI.
What are the SX of otitis media?
Otalgia (ear pain)
Ottorhea (discharge)
Diminished hearing
Fever
What are some bacteria that cause of otitis media?
- Strep pneumonia
- Haemophilus influenza (nonencapsulated)
- Moraxella catarrhalis (mostly in children)
What is the treatment for otitis media?
Amoxicillin
What is the cause of oral cavity infections? Virus/bacteria? Other reasons?
Viral/Bacteria: Usually herpes simplex virus and candida albicans and astinomycosis (which causes actinomuces israelii) - the infections are polymicrobial. Infection due to slow growing anaerobe.
Other: Oral surgery, trauma and poor dental hygiene.
What is usually seen in oral cavity infections?
Swelling of soft tissue along the angle of the jaw and neck or in the oral cavity. May develop draining sinus tract with yellow granules of pus (called sulfur granules).
NOTE: Actinomycosis abscesses grow larger as the disease progresses, often over months. In severe cases, they may penetrate the surrounding bone and muscle to the skin, where they break open and leak large amounts of pus, which often contains characteristic granules (sulfur granules) filled with progeny bacteria.
What is the physiology and structure of actinomyces israelii? Gram stain? Structure? Anaerobic or aerobic or microaerophilic? Speed of growth?
GS: Gram positive rod
Structure: filamentous
Anaerobic/microaerophilic
Slow growing
Where is Actinomyces israelii normally found? (3)
Normal flora of upper respiratory tract, GI tract and female genital tract.
When does Actinomyces israelii cause infection?
Is it part of the normal flora, so it is in an opportunistic pathogen. It only causes disease when mucosal barrier is disrupted.
What diseases do Actinomyces israelii cause? (4)
Oral - cervicofacial (oral cav. infect)
Thoracic disease
Abdominal disease
Pelvic disease - associated with IUD use
How do you diagnose Actinomyces israelii?
Bacteria in the sulfur granules.
What is the treatment for Actinomyces israelii?
Penicillin or amoxicillin for 6-12 months.
What is pharyngitis? How is it caused?
It is a sore throat. Acute pharyngitis most often caused by viruses however bacterial pharyngitis is MCC by S. pyogenes (Group A step).
Who most often gets pharyngitis (age range) and how is it spread?
5-15 year old and it is spread by respiratory droplets.
How does the infection cause phayngitis?
Bacteria attach to the mucosa (s. pyogenes) via M protein.
What are the symptoms associated with pharyngitis?
Sore throat Fever Chills Abdominal Pain Inflamed uvula/pharynx Enlarged tonsils with grayish-white patchy exudate
What is NOT SEEN in pharyngitis?
Cough and congestion are ABSENT
How is s. pyogenes pharyngitis diagnosed?
Rapid strep test. Culture if the test is negative in children only.
What are the possible complication of S. pyogenes pharyngitis?
Glomerulonephritis
Scarlet Fever
Rheumatic Fever
What is the treatment for S. pyogenes pharyngitis?
Amoxicillin
What is epiglottitis and what is its progression?
It is the inflammation of the epiglottis which progresses rapidly. Can cause a potentially fatal obstruction of the airway.
What are the bacteria that most often cause epiglottitis?
HiB
H. parainfluenza
S. pneumonia
S. pyogenes (GAS)
Normal flora
What caused a reduction in epiglottitis cases?
Hib vaccine (reduced infection by H. influenza)
What are some associated SX with epiglottitis?
Severe sore throat
Fever
Dysphagia (difficulty swallowing)
Muffled voice
How do you diagnose epiglottitis?
Clinical SX and blood culture (often + for bacteria)
What is the treatment for epiglottitis?
First need to secure the airway (do not want obstruction) and then cefotaxime (3rd generation cephalosporins)
What is pneumonia?
It is the infection of the lung parenchyma (alvoli, alveolar duct, bronchioles)
What SX are associated with pneumonia?
Cough Fever Tachcardia Dyspnea Chest pain Increased resp. rate Use of accessory muscles
What are the different classification of pneumonia? (5)
- Community-acquired (CAP) - outpatient or within 48 hours of hospital admission
- Hospital-acuired (HAP) (in hospital for MORE than 48 hours)
- Ventilator-associated (VAP)
- Health-care associated (HCAP) - CAP with increased risk of multi-drug resistance (MDR) - nursing home, antibiotic use, prior hospitalization, dialysis, family member with MDR infection
- Aspiration (AP)
What are the TYPICAL causes of CAP?
- S. pneumonia
- H. influenza (non-encapsulated)
- S. aureus (after influenza infection - viral infect)
- CA-MRSA
What SX are seen in CAP?
Fever
Dyspnea
Productive Cough
Chest Pain
What are the ATYPICAL bacterial pathogens that cause CAP? (All cannot be gram stained)
- Legionella pneunophila (stains poorly)
- Mycoplasma pneumonia (lacks cell wall)
- Chlamydophilia pneumonia (lacks peptidoglycan)
What are the zoonotic atypical bacterial pathogens?
- Chlamydophila psittaci (lacks peptidoglycan layer)
2. Francisella tularensis (stains poorly)
What SX are seen in CAP caused by atypical bacterial pathogens?
Cough which is NOT productive as well as extra pulmonary findings.
What does legionella pneumophila pneumonia cause?
Legionnaires disease
How is legionella pneumophila transmitted?
Inhalation of contaminated water vapours (questions are usually associated with recent hotel stays or cruises in which there is an air conditioner system)
